The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
An airplane is moved by several turbojet engines each housed in a nacelle serving to channel the flows of air created by the turbojet engine, which also houses a set of related actuating devices connected to its operation and performing various functions when the turbojet engine is running or stopped.
These related actuating devices in particular comprise a mechanical thrust reversal system and an adaptive nozzle system.
A nacelle generally has a tubular structure comprising an air intake upstream from the turbojet engine, a middle section designed to surround a fan of the turbojet engine, a downstream section housing thrust reversal means and designed to surround the combustion chamber of the turbojet engine, and generally ends with a jet nozzle whereof the outlet is situated downstream from the turbojet engine.
Modern nacelles are designed to house a dual-flow turbojet engine capable of creating, by means of the rotating fan blades, a hot air flow (also called primary flow) coming from the combustion chamber of the turbojet engine, and a cold air flow (secondary flow) that circulates outside the turbojet engine through an annular passage, also called the tunnel, formed between a fairing of the turbojet engine and an inner wall of the nacelle. The two flows of air are discharged from the turbojet engine through the rear of the nacelle.
During landing of an airplane, the role of a thrust reverser is to improve the braking capacity thereof by reorienting at least part of the thrust generated by the turbojet engine forward. In this phase, the reverser covers the cold flow tunnel and orients that cold flow toward the front of the nacelle, thereby creating a counter-thrust that is added to the braking of the wheels of the airplane.
The means used to perform that reorientation of the cold flow vary depending on the type of reverser. However, in most cases, the structure of a reverser comprises movable covers that can be moved between an open or “reverse jet” position, in which they open a passage in the nacelle designed for the deflected flow, on the one hand, and a closed or “direct jet” position, in which they close that passage. These sliding covers may perform a deflection function or simply serve to activate other deflection means.
In the case of a cascade thrust reverser, also called a cascade reverser, the reorientation of the flow of air is done by cascade vanes, the cover performing only a simple sliding function serving to expose or cover said vanes, the translation of the movable cover being done along a longitudinal axis substantially parallel to the axis of the nacelle. Complementary blocking panels, actuated by the sliding of the cover, generally make it possible to close the tunnel downstream of the cascade vanes so as to optimize the reorientation of the cold flow toward the outside of the nacelle.
In addition to its thrust reversal function, the sliding cover belongs to the downstream section of the nacelle and has a downstream portion forming a jet nozzle serving to channel the discharge of the flows of air toward the outside. This nozzle may supplement a primary nozzle channeling the hot flow, and is then called the secondary nozzle.
The thrust reversal performance is obtained in a satisfactory manner with the known devices. However, for improved aerodynamics and fuel consumption reasons, it is very advantageous to be able to adjust the section of the cold air flow outlet downstream of the nacelle. It is in fact useful to be able to increase that section during takeoff and landing phases, and to reduce it during cruising phases: the term “variable fan nozzle” (VFN) is often used.
Such a system is described in documents FR 2 622 929 and FR 2 902 839, for example.
These documents describe the implementation of cascade thrust reversers equipped with an adaptive nozzle and, to that end, provide a movable fairing comprising an upstream portion performing the function of the sliding reverser cover and a downstream portion performing the function of the adaptive nozzle, these two portions being able to be connected to each other by bolt means.
It is important to be able to actuate these two portions of the nacelle independently: it is in particular desirable to be able to increase the section of the adaptive nozzle without actuating the thrust reversal means, in particular during takeoff.
To perform this independent actuation, each moving part (sliding cover/nozzle) can be equipped with its own actuator (two single-rod actuators or a double-rod cylinder, for example) and may be driven independently.
In order to lighten the actuating means, it is possible to use one single-rod actuator, by providing appropriate means for locking/unlocking the adaptive nozzle from the sliding cover.
Such a solution and several implementation principles are presented in document FR 2 902 839, in particular in FIGS. 13 to 15.